In the United States, strabismus (ambliopia) in children is most often corrected by surgical procedures. Non-surgical alternatives such as occlusive eye patches, fresnel eyeglass lenses, and the like are also available and are the first treatment of choice in Europe. The use of self-adhesive occlusive eye patches is quite common.
In occlusive therapy, an eye patch is applied daily over the nonaffected eye of the child. On average, the patch is worn for two hours each day, longer for older children, shorter for young children. There is some evidence in the literature to suggest that the efficacy of occlusive therapy is improved if the occlusive patch can be made so as to effectively prevent the passage of light to the nonaffected eye. The objective of occlusive therapy is to maintain the nonaffected eye (beneath the occlusive patch) immobile while the uncovered affected eye is free to move in response to visual stimuli. It is believed that small amounts of light passing through the occlusive patch to the nonaffected eye stimulate undesirable eye movement, thereby decreasing the efficacy of the treatment.
Criteria for an acceptable self-adhesive occlusive eye patch include the use of a gentle, hypoallergenic adhesive, softness and conformability to the eye socket, breathability, i.e., moisture vapor and air permeability to reduce the potential for skin damage, and cosmetic appeal. Furthermore, a light occlusive patch should effectively block the passage of ambient light without sacrificing any of the above requirements. Prior to the present invention, a self-adhesive occlusive eye patch having this combination of properties was not available.
A product known as Opticlude.RTM. Orthoptic Eye Patch sold by 3M comprises an absorbent pad having nonadherent films on its upper and lower surfaces. A layer of skin-tone nonwoven medical tape, i.e., Micropore.RTM. brand tape, overlies the adherent film on the upper surface of the pad and extends beyond the periphery of the pad in all directions to secure the patch to the eye socket. A removable liner protects the pad and adhesive layer prior to use.
Although Opticlude.RTM. patches meet most of the criteria listed above, they effectively block only about 75 percent of the incoming ambient light. Several years ago attempts were made to modify the Opticlude.RTM. product to make it light occlusive. A stiff, black, light-absorbing polyethylene film layer overcoated with a solid resin layer for skin toning was inserted between the nonwoven tape and the absorbent pad. In field testing, particularly in Germany, these patches reportedly caused skin irritation when worn and/or removed. The source of the irritation appeared to be the stiffness of the black film layer as well as the fact that the black film layer with its skin toned resin overcoat did not have good moisture vapor permeability.
Another product which has attempted to provide light occlusivity is Elastopad-lite occlusive plasters sold in Europe by Beiersdorf. This product is a laminate comprising an adsorbent pad, a layer of black nonwoven material and a layer of porous skin-tone polyvinyl chloride overlying the black nonwoven layer. A piece of skin-toned tape overlies the polyvinyl chloride layer and extends beyond the periphery of the other layers of the patch to adhere the patch to the eye socket. While the Elastopad product is moisture vapor permeable and appears to block virtually all of the ambient light, it is relatively thick, and not sufficiently soft and conformable to insure maximum comfort.
In U.S. Pat. No. 4,793,003, a self adherent eye patch is disclosed which is thin, soft, breathable, conformable and comfortable to wear, and also blocks virtually all incoming light. This combination of desirable properties is provided by fabricating the eye patch from a thin microporous polymeric film which is both capable of blocking at least 95 percent of light in a preselected wavelength and permeable to moisture vapor. The preferred film of this type is a porous polyethylene film made in accordance with U.S. Pat. No. 4,539,256 and rendered light occlusive by the addition of pigment. The eye patch also comprises an absorbent pad and a pressure sensitive adhesive for adhering the eye patch to the skin around the eye.